Method and device to measure perforation tunnel dimensions

Abstract

A method of logging a perforation tunnel and associated features of the perforation tunnel can include the following features. A logging device including an ultrasonic transducer is located downhole into a well. The well has a casing. The ultrasonic transducer has a focal point that is a distance from the ultrasonic transducer so as to be behind the inner face of the casing. An ultrasonic signal is projected from the ultrasonic transducer. A reflection of the ultrasonic signal is reflected from an internal portion of the perforation tunnel, the perforation tunnel extending through the casing and into formation. A transit time is measured between transmission and reception of the ultrasonic signal. A position of the ultrasonic transducer corresponding to the ultrasonic transmission and reception of the reflected signal is determined.

What is claimed is: 
     
       1. A method of logging a perforation tunnel and associated features of the perforation tunnel, comprising:
 a) locating a logging device including an ultrasonic transducer into a well, the well having a casing, the ultrasonic transducer having a focal point that is a distance from the ultrasonic transducer so as to be behind the inner face of the casing; 
 b) projecting an ultrasonic signal from the ultrasonic transducer; 
 c) detecting a reflection of the ultrasonic signal from an internal portion of the perforation tunnel, the perforation tunnel extending through the casing and into formation; 
 d) measuring a transit time between transmission and reception of the ultrasonic signal; 
 e) determining a position of the ultrasonic transducer corresponding to the ultrasonic transmission and reception of the reflected signal; 
 f) repeating steps b)-e) multiple times and recording resultant data; 
 g) processing the resultant data with a computer and determining a dimension of the perforation tunnel; and 
 wherein the ultrasonic transducer is located a standoff distance from the wellbore casing at least one-third of a length of a minimum open tunnel length required to measure; 
 the standoff distance being so that reflections from the casing reverberate and substantially dissipate before a reflection from inside the perforation tunnel is received by the ultrasonic transducer. 
 
     
     
       2. A method of  claim 1 , wherein the ultrasonic signal is within a range of 500 kHz to 5000 kHz. 
     
     
       3. A method of  1 , wherein the ultrasonic signal is within a range of 300 kHz to 3000 kHz. 
     
     
       4. A method of  1 , wherein the ultrasonic signal is approximately 1000 kHz. 
     
     
       5. A method of  claim 1 , comprising processing the resultant data with a computer and determining a dimension of debris in the perforation tunnel. 
     
     
       6. A method to detect perforation tunnels and associated features of the perforation tunnels, comprising:
 a) lowering an ultrasonic transducer into a wellbore, the wellbore having a casing lining the wellbore, a perforation tunnel extending through the casing and into the formation; 
 b) positioning the ultrasonic transducer adjacent to and facing into the perforation tunnel, the ultrasonic transducer being a standoff distance from the casing so that reflections from the casing reverberate and substantially dissipate before a reflection from inside the perforation tunnel is received by the ultrasonic transducer; 
 c) projecting an ultrasonic signal; 
 d) detecting a reflection of the ultrasonic signal reflected from an internal portion of the perforation tunnel; 
 e) detecting a reflection of the ultrasonic signal reflected from the inside surface of the casing; 
 f) measuring transit times and amplitudes of the reflection from the casing and of the reflection from inside the perforation tunnel; 
 repeating steps b)-f) and recording the resultant data; 
 processing the resultant data with a computer and determining a depth of the perforation tunnel and a dimension of debris in the perforation tunnel. 
 
     
     
       7. The method of  claim 6 , comprising determining a position of the ultrasonic transducer corresponding to the ultrasonic transmission and reflection reception. 
     
     
       8. The method of  claim 6 , wherein the standoff distance is at least one-third a length of a minimum open tunnel length required to measure. 
     
     
       9. The method of  claim 7 , further comprising: configuring the signal diameter to be equal to or less than an expected width of an opening in the casing at the opening of the perforation tunnel. 
     
     
       10. A method of  claim 6 , wherein the ultrasonic transducer is a focused ultrasonic transducer and is focused at a point behind an inside surface of the casing. 
     
     
       11. A method of  claim 10 , wherein the signal diameter is determined by way of the following formula:
   Signal Diameter(−6 dB)=(1.02* Fc )/ fD , wherein
 
 F is the focal length of the transducer; 
 C is the sound speed in the wellbore fluid; 
 f is the frequency of the transducer; 
 D is the diameter of the transducer element in SI units. 
 
     
     
       12. A method of determining a depth of a perforation tunnel, comprising:
 lowering a logging device into a wellbore, the wellbore having a casing that lines the wellbore; 
 a perforation comprising a tunnel that extends through the casing into formation; 
 the logging device comprising an ultrasonic transducer; 
 positioning the ultrasonic transducer adjacent to the perforation so as to overlap the perforation in a direction extending along a central longitudinal axis of the perforation; 
 emitting an ultrasonic signal from the ultrasonic transducer into the perforation; 
 receiving reflections of the ultrasonic signal from inside the perforation tunnel; and 
 determining the depth of the perforation tunnel and a dimension of debris in the perforation tunnel. 
 
     
     
       13. The method of  claim 12 , comprising:
 using a processor to determine the depth of the perforation tunnel based on the signal received from reflecting inside the perforation. 
 
     
     
       14. A method of  claim 12 , comprising:
 presenting the depth of the perforation tunnel on a digital visual display. 
 
     
     
       15. A method of  claim 1 , wherein the perforation tunnel has a circular cross section. 
     
     
       16. The method of  claim 6 , wherein the perforation tunnel has a circular cross section. 
     
     
       17. The method of  claim 12 , wherein the perforation has a circular cross section. 
     
     
       18. The method of  claim 1 , wherein the perforation tunnel has a tapered cylindrical shaped volume. 
     
     
       19. The method of  claim 6 , wherein the perforation tunnel has a tapered cylindrical shaped volume. 
     
     
       20. The method of  claim 12 , wherein the perforation has a tapered cylindrical shaped volume. 
     
     
       21. A method of logging a perforation tunnel and associated features of the perforation tunnel, comprising:
 a) locating a logging device including an ultrasonic transducer into a well, the well having a casing, the ultrasonic transducer having a focal point that is a distance from the ultrasonic transducer so as to be behind the inner face of the casing; 
 b) projecting an ultrasonic signal from the ultrasonic transducer; 
 c) detecting a reflection of the ultrasonic signal from an internal portion of the perforation tunnel, the perforation tunnel extending through the casing and into formation; 
 d) measuring a transit time between transmission and reception of the ultrasonic signal; 
 e) determining a position of the ultrasonic transducer corresponding to the ultrasonic transmission and reception of the reflected signal; 
 f) repeating steps b)-e) multiple times and recording resultant data; 
 g) processing the resultant data with a computer and determining a dimension of the perforation tunnel and a dimension of debris in the perforation tunnel. 
 
     
     
       22. A method of  claim 21 , wherein the ultrasonic transducer is located a standoff distance from the wellbore casing at least one-third of a length of a minimum open tunnel length required to measure. 
     
     
       23. A method of  claim 22 , wherein the standoff distance being so that reflections from the casing reverberate and substantially dissipate before a reflection from inside the perforation tunnel is received by the ultrasonic transducer. 
     
     
       24. A method of  claim 21 , wherein the ultrasonic signal is within a range of 500 kHz to 5000 kHz. 
     
     
       25. A method of  21 , wherein the ultrasonic signal is within a range of 300 kHz to 3000 kHz. 
     
     
       26. A method of  21 , wherein the ultrasonic signal is approximately 1000 kHz.